/*
 * Copyright 2023 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.firebase.sessions

import javax.inject.Inject
import javax.inject.Singleton

/**
 * The [SessionGenerator] is responsible for generating the Session ID, and keeping the
 * [SessionDetails] up to date with the latest values.
 */
@Singleton
internal class SessionGenerator
@Inject
constructor(private val timeProvider: TimeProvider, private val uuidGenerator: UuidGenerator) {
  /**
   * Generates a new session.
   *
   * If a current session is provided, will maintain the first session id and appropriate index.
   */
  fun generateNewSession(currentSession: SessionDetails?): SessionDetails {
    val newSessionId = generateSessionId()
    return SessionDetails(
      sessionId = newSessionId,
      firstSessionId = currentSession?.firstSessionId ?: newSessionId,
      sessionIndex = currentSession?.sessionIndex?.inc() ?: 0,
      sessionStartTimestampUs = timeProvider.currentTime().us,
    )
  }

  private fun generateSessionId() = uuidGenerator.next().toString().replace("-", "").lowercase()
}
